Catheter and method of manufacture

ABSTRACT

The instant invention relates generally to introducer catheters used to help deliver catheters or other medical devices to locations within the human body. In particular, the instant invention relates to large diameter introducer catheters (introducer catheters with lumens greater than about 6 French) having increased strength, flexibility, and kink resistance. Introducer catheters according to the teachings herein may also include curved distal ends and flared (that is, funnel-like) transition sections within their lumens.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/978,719, filed 22 Dec. 2015, now U.S. Pat. No. 10,923,139, which is acontinuation of U.S. application Ser. No. 12/527,332, filed 17 Dec.2009, now U.S. Pat. No. 9,254,374, which is a national stage applicationof international application no. PCT/US2008/054149, filed 15 Feb. 2008,now expired, which claims the benefit of U.S. provisional applicationNo. 60/901,344, filed 15 Feb. 2007. Each of the foregoing is herebyincorporated by reference as though fully set forth herein.

BACKGROUND OF THE INVENTION a. Field of the Invention

The instant invention relates generally to catheters and to introducercatheters used to help deliver catheters or other medical devices tolocations within the human body. In particular, the instant inventionrelates to catheters and introducer catheters having a torque transferlayer configured to provide increased strength, flexibility, and kinkresistance.

b. Background Art

Catheters are used for an ever growing number of medical procedures. Toname just a few examples, catheters are used for diagnostic,therapeutic, and ablative procedures. Typically, the physicianmanipulates the catheter through the patient's vasculature to theintended site, such as a site within the patient's heart. The cathetertypically carries one or more electrodes or other diagnostic ortherapeutic devices, which may be used for ablation, diagnosis, cardiacmapping, or the like.

It is known that, to facilitate placement of the diagnostic ortherapeutic catheter at a location of interest within the patient, itmay be introduced through another catheter, commonly known as a “guidingcatheter” or “introducer catheter,” and the terms will be usedinterchangeably herein. Generally speaking, an introducer catheter is atube having a high degree of directional control that is used to placeother catheters, which may have little or no directional control, intospecific areas of the patient's body.

In the field of cardiac ablation, for example, introducer catheters maybe used to negotiate the patient's vasculature such that an ablationdevice may be passed therethrough and positioned to ablatearrhythmia-causing cardiac tissue. The introducer catheter itself may beadvanced over a guide wire.

Generally, it is known that the introducer catheter must have an overalldiameter small enough to negotiate blood vessels while retaining aninner diameter (or “bore size”) large enough to accommodate the ablationdevice therethrough. Furthermore, since the path within the patient isoften long and tortuous, steering forces must be transmitted overrelatively great distances. Accordingly, it is desirable for theintroducer catheter to have sufficient axial strength to be pushedthrough the patient's vasculature via a force applied at its proximalend (“pushability”). It is also desirable for the introducer catheter totransmit a torque applied at the proximal end to the distal end(“torqueability”). An introducer catheter should also have sufficientflexibility to substantially conform to the patient's vasculature andyet resist kinking as it does so. One of ordinary skill in the art willrecognize that these various characteristics are often in tension withone another, with improvements in one requiring compromises in others.For example, increasing the bore size of an introducer catheter having agiven overall diameter requires utilizing a thinner wall. A thin-walledintroducer, however, is more likely to collapse upon itself when atorque is applied at its proximal end.

To improve pushability, torqueability, flexibility, and kink resistance,many extant introducer catheters utilize one or more reinforcing layersin their construction. For example, the guiding catheter disclosed inU.S. Pat. No. 4,817,613 to Jaraczewski et al. (“Jaraczewski”) includes apair of braided torque transmitting layers sandwiched between a flexibletubular member and a flexible plastic casing applied as a viscousmaterial and subsequently cured. Jaraczewski also teaches, however, thatto a certain degree, flexibility comes at the expense of torqueability.Further, depending on the thickness of the torque transfer layers, theymay increase the wall thickness, thereby either increasing the overalldiameter of the introducer catheter for a given bore size or decreasingthe bore size for a given overall diameter.

Many extant large bore introducers (i.e., an introducer catheter withbore size of greater than about 6 French), in order to find a suitablebalance of pushability, torqueability, flexibility, and kink resistance,have outer layers that are relatively stiff, which compromisestorqueability, kink resistance, and flexibility for pushability.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention provide a catheter, particularly anintroducer catheter, having good pushability, torqueability,flexibility, and kink resistance, while retaining a large bore size fora given overall diameter. In specific embodiments, an introducercatheter with good pushability, torqueability, flexibility, and kinkresistance has a bore size of at least about 6 French and an overalldiameter suitable for use in cardiac diagnostic and therapeuticprocedures. The invention further provides a method of constructing acatheter or introducer catheter that does not require compromising someof the characteristics of pushability, torqueability, flexibility, andkink resistance for others of those characteristics.

Disclosed herein is an introducer catheter having a distal end and aproximal end, including: a polymeric inner liner having a substantiallycylindrical distal section, a substantially cylindrical proximalsection, and a frusto-conical intermediate section between the distalsection and the proximal section; a torque transfer layer surrounding atleast a portion of the inner liner; and an outer sheath of amelt-processable polymer formed over the torque transfer layer. Theinner liner defines a lumen, which may desirably have a diameter of atleast about 12 French.

In some embodiments, the distal section of the inner liner defines adistal section of the lumen and the proximal section of the inner linerdefines a proximal section of the lumen, and the diameter of the distalsection of the lumen is smaller than the diameter of the proximalsection of the lumen. For example, the diameter of the proximal sectionof the lumen may be between about 0.004″ and about 0.005″ greater thanthe diameter of the distal section of the lumen. As another example, thediameter of the distal section of the lumen may be about 12.5 French andthe diameter of the proximal section of the lumen may be about 14French. Typically, the slope of the frusto-conical intermediate sectionis between about 4 degrees and about 6 degrees, more preferably about 5degrees.

Optionally, the torque transfer layer includes at least two flat wiresbraided into a wire mesh. A braid density of the torque transfer layermay vary along a length of the introducer catheter, such as being higheradjacent the intermediate section of the inner liner than elsewherealong the length of the introducer catheter.

Optionally, the distal end of the introducer catheter may be shaped in apreset curvature.

Also disclosed herein is a method of manufacturing an introducercatheter having a distal end and a proximal end. The method generallyincludes the steps of: forming a polymeric inner liner about a mandrelhaving an outer diameter that varies along a length of the mandrel,wherein the mandrel has a substantially cylindrical proximal section, asubstantially cylindrical distal section, and a frusto-conicaltransition section between the proximal section and the distal section;forming a torque transfer layer over at least a portion of the innerliner, the torque transfer layer including a plurality of flat wiresbraided into a wire mesh; forming an outer sheath about the torquetransfer layer, the outer sheath comprising a melt-processable polymer;applying energy to the outer sheath to bond the outer sheath to thetorque transfer layer and the inner liner; and removing the mandrel,thereby creating a lumen in the introducer catheter, the lumen having aproximal section having a first diameter, a distal section having asecond diameter less than the first diameter, and a frusto-conicaltransition section between the proximal section and the distal section.Optionally, the method further includes the step of forming the distalend of the introducer catheter into a preset curvature.

In another aspect of the invention, an introducer catheter having adistal end and a proximal end includes: a tubular polymeric inner linerhaving a lumen diameter of at least about 8 French; a torque transferlayer surrounding at least a portion of the inner liner, the torquetransfer layer comprising at least two flat wires braided into a wiremesh; and an outer sheath of a melt-processable polymer formed over thetorque transfer layer, wherein the outer sheath includes a distalsegment and a proximal segment, the proximal segment having a higherdurometer than the distal segment, and wherein the distal end of theintroducer catheter is formed into a preset curvature.

The distal segment may include a frusto-conical tip segment and asubstantially cylindrical intermediate segment positioned between thetip segment and the proximal segment, with the intermediate segmenthaving a durometer that is intermediate to the tip segment and theproximal segment.

It is desirable for the outer diameter of the outer sheath to be lessthan about 11 French, more preferably less than about 10 French.

A radius of the preset curvature is preferably between about 0.8″ andabout 1.2″, and an arc of the preset curvature is preferably betweenabout 25 degrees and about 45 degrees. More preferably, the radius ofthe preset curvature is between about 0.9″ and about 1.1″ and the arc ofthe preset curvature is between about 30 degrees and about 40 degrees.Most preferably, the radius of the preset curvature is about 1.0″ andthe arc of the preset curvature is about 35 degrees.

In some embodiments, the introducer catheter further includes a flaredtransition section proximate the proximal end, the lumen diameter of theinner liner proximate of the flared transition section being larger thanthe lumen diameter of the inner liner distal of the flared transitionsection. For example, the flared transition section may be afrusto-conical transition section. The lumen diameter of the inner linerproximal of the flared transition section is preferably between about0.004″ and about 0.005″ greater than the lumen diameter of the innerliner distal of the flared transition section.

In still another aspect, the present invention provides a method ofmanufacturing an introducer catheter having a distal end and a proximalend, generally including the following steps: forming a tubularpolymeric inner liner about a mandrel, the mandrel having an outerdiameter of at least about 8 French; forming a torque transfer layerover at least a portion of the inner liner, the torque transfer layerincluding a plurality of flat wires braided into a wire mesh; forming anouter sheath about the torque transfer layer, the outer sheath includingat least a distal segment and a proximal segment, wherein each of thedistal segment and the proximal segment comprises a melt-processablepolymer, and wherein a hardness of the proximal segment is greater thana hardness of the distal segment; heating the inner liner, the torquetransfer layer, and the outer sheath to a temperature sufficient to bondthe outer sheath to the torque transfer layer and the inner liner;forming the distal end of the introducer catheter into a presetcurvature; and removing the mandrel.

The step of forming an outer sheath about the torque transfer layer mayinclude abutting the distal segment of the outer sheath and the proximalsegment of the outer sheath such that the distal segment of the outersheath bonds to the proximal segment of the outer sheath during theheating step. Alternatively, the step of forming an outer sheath aboutthe torque transfer layer may include overlapping the distal segment ofthe outer sheath and the proximal segment of the inner sheath such thatthe distal segment of the outer sheath bonds to the proximal segment ofthe outer sheath during the heating step. In still other embodiments,the step of forming an outer sheath about the torque transfer layer mayinclude extruding the outer sheath about the torque transfer layer suchthat the melt-processable polymer of the outer sheath occupies aplurality of voids of the wire mesh in the torque transfer layer.

Of course, the distal segment of the outer sheath may include a tipsegment and an intermediate segment positioned between the tip segmentand the proximal segment of the outer sheath. The tip segment may be afrusto-conical segment.

The foregoing and other aspects, features, details, utilities, andadvantages of the present invention will be apparent from reading thefollowing description and claims, and from reviewing the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an introducer assembly in accordancewith one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a steerable, large bore introducercatheter in accordance with an embodiment of the present invention.

FIG. 3 depicts a reflow mandrel assembly used in the method ofmanufacturing introducer catheters in accordance with the presentinvention.

FIG. 4 depicts an inner layer disposed over a reflow mandrel assembly inaccordance with a preferred method of manufacture.

FIG. 5 depicts a torque transfer layer disposed over an inner layer inaccordance with a preferred method of manufacture.

FIG. 6 depicts an outer sheath of varying components disposed over atorque transfer layer in accordance with a preferred method ofmanufacture.

FIG. 7 depicts the components of an introducer catheter assembled over areflow mandrel assembly having a distal configuration for a tipassembly.

FIG. 8 depicts a tip component, having a radiopaque marker, attached tothe distal end of the introducer catheter depicted in FIG. 7.

FIG. 9 depicts another tip component, having a radiopaque marker,attached to the distal end of the introducer catheter depicted in FIG.7.

FIG. 10 is a perspective view of a steerable introducer catheter inaccordance with an embodiment of the present invention, cut away to showdetails of the steering ring.

FIG. 11 is a perspective view of an introducer assembly in accordancewith another embodiment of the present invention.

FIG. 12 is a sectional view of the introducer assembly of FIG. 11.

FIG. 13 is a cross-sectional view taken along line 13-13 in FIG. 12.

FIG. 14 illustrates the proximal end of an introducer catheter includinga flared transition section.

FIG. 15 is a cross-sectional view taken along line 15-15 in FIG. 14.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a catheter and a large bore introducercatheter suitable for use in the human vasculature for known medicalprocedures, such as cardiac ablation. For purposes of description, thepresent invention will be described in connection with a flat wireguided, or steerable, introducer catheter. It is contemplated, however,that the described features may be incorporated into any number ofcatheters or introducer catheters as would be appreciated by one ofordinary skill in the art. The large bore introducer catheter iscomprised of a combination of components and manufactured by either areflow process or an extrusion process, which provide the surprisingbenefits of allowing for introducer catheters having an internaldiameter of at least about 6 French while maintaining the desirableimproved properties of pushability, torquability, and flexibility, forouter diameters of sufficient size for navigation of cardiacvasculature.

FIG. 1 is a perspective view of an introducer assembly 110 according toone embodiment of the present invention comprising an introducercatheter 100 having a distal end 190 and a proximal end 104. Theintroducer catheter 100 may be operably connected to a handle assembly106 which assists in guiding or steering the introducer duringprocedures. The introducer assembly 110 further includes a hub 108operably connected to an inner lumen (not shown) within the handleassembly 106 for insertion or delivery of catheter assemblies, fluids,or any other devices known to those of ordinary skill in the art.Optionally, the introducer assembly 110 further includes a valve 112operably connected to the hub 108.

FIG. 2 depicts a cross-sectional view of an introducer catheter 200 inaccordance with one embodiment of the present invention. The introducercatheter 200 is comprised of a tubular polymeric inner liner 202, atorque transfer layer 204, an outer sheath 206 comprised of amelt-processable polymer, and a heat shrink layer 208. In the instancewhere the introducer is a steerable introducer, the introducer catheter200 further includes at least one flat wire 210 disposed longitudinallyalong the length of the introducer catheter 200. For purposes of thisinvention, a “flat wire” refers to a wire that is characterized by across-section that, when measured along two orthogonal axes, issubstantially flat. A flat wire typically has a rectangular crosssection, though the cross section need not be perfectly rectangular. Forexample, the present invention contemplates that a cross section of theflat wire may be oval, provided that the overall cross section isgenerally flat. As the term is used herein, a wire may be properlycharacterized as a flat wire if it has a cross section that is measuredx in one direction and at least 2× in a second direction generallyorthogonal to the first direction. A wire whose cross section issubstantially I-shaped may also be a flat wire if, generally, its heightis substantially greater than its width at its widest measurement. Oneof ordinary skill will appreciate that a flat wire may be defined in thecontext of the overall teachings of this application.

The at least one flat wire 210 may be further encased inside anotherpolymeric tubular member 212 forming a lumen 214 for housing the flatwire 210. The introducer catheter according to this embodiment ismanufactured by a reflow bonding process in which the components areindividually fed over a mandrel as discussed in more detail below.

The inner liner 202 is preferably a polymeric material, such aspolytetrafluoroethylene (PTFE) or etched PTFE. The inner liner 202 mayalso be made of other melt processable polymers, including, withoutlimitation, polyether block amides, nylon and other thermoplasticelastomers. Once such elastomer is Pebax® made by Arkema, Inc. Pebax ofvarious durometers may also be used, including without limitation, Pebax30 D to Pebax 70 D. In a preferred embodiment, the inner liner 202 ismade of a material with a melting temperature higher than the outersheath 206 such that the inner liner 202 will withstand the meltprocessing of the outer sheath 206.

Inner liner 202 defines a lumen 216 therethrough, preferably having adiameter 218 of at least about 6 French, more preferably of at leastabout 7 French, and most preferably of between about 10 French and about24 French. However, in some embodiments of the invention, it iscontemplated that lumen 216 may have a diameter 218 of up to about 32French or more, such as between about 7 French and about 32 French.

A torque transfer layer 204 is preferably disposed between the innerliner 202 and the heat shrink layer 208, more preferably between theouter sheath 206 and the inner liner 202. In the instance where theintroducer is a steerable introducer utilizing, for example, at leastone longitudinal wire 210, the torque transfer layer 204 may be disposedbetween either the inner layer 202 and the outer sheath 206 or the outersheath 206 and the heat shrink layer 208. The torque transfer layer 204may be made of stainless steel (304 or 316) wire or other acceptablematerials known to those of ordinary skill in the art.

The torque transfer layer 204 is preferably formed of a braided wireassembly comprised of flat wires, preferably stainless steel wiresincluding, for example, high tensile stainless steel wires. The torquetransfer layer 204 may be formed in any number of known braid patterns,including one-over-one (involving at least two wires) or two-over-two(involving at least four wires) crossover patterns. For lumen diametersof at least about 6 French, braided flat wires of at least about 0.003″thick by at least about 0.007″ wide, which heretofore were not used toform a wire mesh for the torque transfer layer, have producedsurprisingly good results of increased pushability, torqueability,flexibility, and kink resistance over non-flat wires and smaller flatwires. In general, the individual wires have a ratio of width to thethickness of at least about 2:1, including, for example, 2:1 to 5:1.Flat wires of about 0.004″ thick by about 0.012″ wide and of about0.004″ thick by about 0.020″ wide have also been braided with success toform torque transfer layers of superior performance. Of course, otherwire sizes, such as at least about 0.002″ thick by about 0.006″ wide,may also be utilized without departing from the spirit and scope of thepresent invention.

The braid density, commonly measured in pixels per inch (“PPI”), istypically between about 5 and about 100, and will depend on the size ofthe flat wires as well as the size of the catheter. For flat wires of atleast about 0.003″ thick by about 0.007″ wide and a catheter having aninner lumen of at least about 6 French, the braid density is preferablybetween about 10 PPI and about 90 PPI, more preferably between about 10PPI and about 55 PPI. For example, the braid density for flat wires ofabout 0.003″ thick by about 0.007″ wide is preferably between about 20PPI and about 90 PPI, more preferably between about 35 PPI and about 55PPI for an inner lumen of at least 6 French, and most preferably betweenabout 35 PPI and about 45 PPI for an inner lumen of at least about 10French. The braid density for flat wires of about 0.004″ thick by about0.012″ wide is preferably between about 15 PPI and about 70 PPI, andmore preferably between about 15 PPI and about 22 PPI for an inner lumenof at least about 6 French. The braid density for flat wires of about0.004″ thick by about 0.020″ wide is preferably between about 5 PPI andabout 50 PPI, and more preferably between about 10 PPI and about 20 PPIfor an inner lumen of at least about 6 French, and most preferablybetween about 10 PPI and about 20 PPI for an inner lumen of at leastabout 16 French.

Alternatively, the torque transfer layer 204 may utilize a varying braiddensity construction along the length of the introducer catheter 200.For example, the torque transfer layer may be characterized by a firstbraid density at the proximal end of the introducer catheter 200 andthen transition to one or more braid densities as the torque transferlayer 204 approaches the distal end of the introducer catheter 200; thebraid density of the distal end may be greater or less than the braiddensity at the proximal end. In a specific example, the braid density atthe proximal end is about 50 PPI and the braid density at the distal endis about 10 PPI. In another embodiment, the braid density at the distalend is about 20-35% of the braid density at the proximal end.

The torque transfer layer 204 may be formed separately on a disposablecore and subsequently slipped around the inner liner 202. One or moreportions of the torque transfer layer 204 may be heat tempered andcooled before incorporation into the introducer body 200 through methodsthat are known to those of ordinary skill. The action of heat temperingmay help to release the stress on the wire and help reduce radialforces. It is also contemplated that torque transfer layer 204 may bebraided directly on the inner liner 202.

A particularly preferred torque transfer layer 204 is comprised of0.003″ by 0.007″ 304 stainless steel wires at 35 PPI for an inner lumenof 6-10 French. Another preferred torque transfer layer 204 is comprisedof 0.004″ by 0.012″ 304 stainless steel wires at 22 PPI for an innerlumen of 12 French. Yet another preferred torque transfer layer 204 iscomprised of 0.004″ by 0.020″ 304 stainless steel wires at 13 PPI for aninner lumen of 16 French. These particularly preferred torque transferlayers may be manufactured on a commercially available horizontal braidmachine set at 225 rpm utilizing a commercially available mandrel. Othersuitable methods of manufacturing the torque transfer layer 204 will beapparent to those of ordinary skill in the art.

The outer sheath 206 is preferably either an extruded Pebax or PTFEtubing. The melt-processable polymer of the outer sheath 206 occupies aplurality of voids of the wire mesh in the torque transfer layer 204.The outer sheath 206 may also be made of other melt processablepolymers, including, without limitation, etched PTFE, polyether blockamides, nylon and other thermoplastic elastomers, at varying durometers.The outer sheath 206 may also comprise more than one layer, including,for example, two or more tubes of a melt processable polymer.Alternatively, as shown in FIG. 6, the outer sheath 306 may be comprisedof varying segments 322, 324, 326, 328, 330 differing in hardness and/ormaterial along the length of the introducer 300 and being reflow bondedtogether. This may be accomplished by layering or by placing annularrings of differing materials along the length of the introducer 300.Varying the sheath composition in this manner provides the additionalbenefit of adjusting flexibility, torquability, and pushability atvarious points along the introducer 300.

In embodiments where the introducer is a steerable introducer (as shownin FIG. 2), at least one flat wire 210 is provided, preferably extendingalong substantially the entire length of the introducer. The flat wire210 is preferably composed of stainless steel and is preferably about0.002″×about 0.006″, and more preferably about 0.004″×about 0.012″ or0.016″. The flat wire may be selected such that the ratio of the widthto thickness is at least about 2:1. In one embodiment, at least aportion of the flat wire is encased inside a preformed tube 212 beforeplacement along the inner liner 202 to form a flat lumen 214. Thepreformed tube 212 need not be the same shape as the cross section ofthe flat wire, but instead, may be round, oval, rectangular, or anotherlike shape. Preferably, the preformed tube 212 has a cross section thatis not the same shape as a cross section of the flat wire 210, in orderto facilitate movement of the flat wire in the preformed tube. Thepreformed tube may be formed of PTFE, etched PTFE, polyether blockamides (such as Pebax), nylon, other thermoplastic elastomers, or anyother known material to one of ordinary skill in the art. Preferably,the preformed tube 212 has a higher melting point than the outer sheath206 so that the preformed tube 212 will not melt when the introducercatheter 200 is subjected to melt processing. In alternative embodimentsthe flat wire 210 may be covered with lubricious materials (not shown)before placement, including silicone and other lubricious materials.Alternatively, the flat wire 210 may also be coated with a lubriciouslayer to promote slideability, and it is also contemplated that the flatwire 210 may be manufactured with a smooth surface to promoteslideability. While stainless steel is a preferred material to composethe flat wire 210, other materials may be used, including, withoutlimitation, materials that are used for conventional round pull wires.More than one flat wire 210 may also be used, and in such cases, eachsuch flat wire 210 may be encased inside its own flexible tube 212.Preferably, as shown in FIG. 2, a pair of flat wires 210 are used thatare spaced at 180 degrees apart. The flat wires 210 are preferablyconnected to at least one steering ring 90 typically located near thedistal end of the introducer (see, e.g., FIG. 10). The proximal ends ofthe flat wires 210 are then operably connected to a steering mechanism(not shown) allowing for manipulation, or steering, of the introducercatheter 200 during use. FIG. 10 shows a cutaway view of the introducercatheter 200 according to the present invention highlighting thesteering ring 90 and its connection to the pull wires 210.

The basic method of manufacture according to an embodiment of thepresent invention will be described in reference to FIGS. 3-9. As thevarious components are assembled, the introducer components will becollectively referred to as an introducer. As depicted in FIGS. 3-9, amandrel 300, which is preferably round in cross-section and preferablyfrom about 6 inches to about 4 feet in length, is provided. As depictedin FIG. 3, the mandrel 300 has a distal end 350 and a proximal end 352.As depicted in FIG. 4, an inner liner 302 is placed on the mandrel 300.The inner liner 302 is fed on to the mandrel 302 and is then knotted onone end 320, or both ends.

As depicted in FIG. 5, a torque transfer layer 304 is then placed overthe inner liner 302. In the case of a steerable introducer catheter, theflat wire assembly (not shown) may then be placed over the torquetransfer layer 304. Alternatively, the flat wire assembly may be placedover an outer sheath 306. Another sheath layer (not shown) mayadditionally be placed over the flat wire assembly. The torque transferlayer terminates proximally of the distal end of the catheter.

Next, as depicted in FIG. 6, an outer sheath 306 is placed over thetorque transfer layer 304 and may be made of either single or multiplesections of tubing that are either butted together or overlapped witheach other. The multiple segments, or layers, of sheath material may beany length and/or hardness (durometer) allowing for flexibility ofdesign. FIG. 6 identifies a plurality of segments, 322, 324, 326, 328and 330. In this embodiment, the proximal end 330 of the outer sheath306 may be made of a material such as nylon, and the remainder of theintroducer may be made of one or more Pebax materials. The lengths ofthe various segments may vary, but preferably, the durometer hardnesslevels will decrease as the outer sheath 306 approaches its distal end.For example, a nylon base may then be followed by one or more of thefollowing Pebax segments: 70 D Pebax; 60 D Pebax; 55 D Pebax; 40 DPebax; 35 D Pebax; 30 D Pebax. The introducer shaft may also use one ormore blends of the foregoing Pebax materials, including, for example, 70D/60 D Pebax blend made by co-extrusion, or a 40 D/35 D Pebax blend madeby co-extrusion. Preferably, the various components of the outer sheath306 according to this embodiment will be reflowed together duringmanufacturing. The proximal end of the shaft is preferably the longestsegment, and more distal segments may preferably vary between 0.25″ to6″, and more preferably from 0.25″ to about 3″. Preferably, the hardnesslevels of the segments and the lengths of the segments may be adjustedfor specific applications, and preferably, the distal end may have thelowest durometer levels of all segments. The shaft segments may beselected to improve flexibility, torquability, and pushability for thespecific application, as appreciated by one of ordinary skill in theart. Alternatively, the catheter may be formed by placing a thin innerjacket or layer (e.g., PTFE layer) onto a mandrel (e.g., stainless steelmandrel) or extruding a thin inner jacket or layer (e.g., Pebax layer)onto an extrusion mandrel (e.g., acetal mandrel), forming a torquetransfer layer over the inner layer, and extruding an outer jacket orsheath (e.g., Pebax jacket) over the torque transfer layer.

Lastly, a heat shrink layer 308 is placed over the assembled introducerassembly prior to reflow lamination. The heat shrink layer 308 ispreferably a fluoropolymer or polyolefin material, such as FEP, or othersuitable material as appreciated by one of ordinary skill in the art.

After assembly of the various components, the introducer assembly 300 issubjected to a reflow lamination process. FIG. 2 depicts a crosssectional view of the introducer assembly after this reflow process.Introducer assembly 200 may be laminated by heating the assembly untilthe material comprising the outer sheath 206 flows and redistributesaround the circumference. Preferably, the heat shrink layer 208 has ahigher melt temperature than the outer sheath 206, and during the meltprocess, the heat shrink layer 208 retains its tubular shape and forcesthe liquefied sheath layer material 206 into the torque transfer layer204 and into contact with the flat wires 210/preformed tubes 212 (ifpresent) and the inner liner 202. The introducer assembly 200 may thenbe cooled. The mandrel is preferably left in place during the coolingprocess as it helps the introducer assembly to retain its inner lumen ofat least about 6 French. The heat shrink layer 208 may be left on theintroducer assembly 200, or optionally removed. If the heat shrink layer208 is removed, the outer sheath 206 becomes the outside layer of theintroducer catheter 200.

Additionally, as shown in FIGS. 7-9, the present invention contemplatesthe inclusion of a tip assembly for use in medical procedures, such asan atraumatic tip, including, for example, a radiopaque materialcontained therein for location of the tip during use. For example, FIGS.7-9 depict a cross section of an introducer catheter 700 having a distalportion 730 configured to accept a tip assembly 732 or 734. In bothexamples, the tip 732 or 734 includes a ring 736, e.g., a radiopaquemarker, for location of the tip 732 or 734 during use. Additionally,FIG. 9 further includes a tip assembly 734 configured with a pluralityof port holes 738 for delivery of, for example, irrigation fluid. Thetip assembly may further be configured with ablation electrodes (notshown) operably connected to a power supply (not shown), for use incardiac ablation procedures.

Another embodiment of the present invention is depicted as introducerassembly 800 in FIGS. 11-13. Introducer assembly 800 includes anintroducer catheter 810 having a distal end 890 and a proximal end 804.Similar to the embodiment illustrated in FIG. 1, introducer catheter 810may be operably coupled to a hub 108, which is operably connected toinner lumen 216 (FIGS. 12 and 13) for insertion or delivery of catheterassemblies, fluids, or any other devices known to those of ordinaryskill in the art. Hub 108 may in turn be operably coupled to a valve112.

As shown in FIG. 12, introducer catheter 810 includes inner liner 202,torque transfer layer 204, and outer sheath 206, as well as radiopaquemarker 736, as described in detail above. Torque transfer layer 204 mayterminate proximally of distal end 890 of introducer catheter 810 asshown, or may extend substantially the entire length of introducercatheter 810. Inner liner 202 may also terminate proximally of distalend 890 of introducer catheter 810 as shown or extend substantially theentire length thereof.

Preferably, the inner diameter 218 (FIG. 13) of inner liner 202 is atleast about 8 French, while the outer diameter 250 of outer sheath 206is less than about 11 French, more preferably less than about 10 French.Of course, the inner and outer diameters of introducer catheter 810 maybe varied by one of ordinary skill in the art in accordance with theprinciples disclosed herein in order to adapt introducer catheter 810for various surgical applications, therapeutic applications, diagnosticapplications, and the like.

Outer sheath 206 includes a proximal segment 206 a, an intermediatesegment 206 b, and a tip segment 206 c. Intermediate segment 206 b andtip segment 206 c may be collectively referred to as a “distal segment”to distinguish them from proximal segment 206 a. In some embodiments ofthe invention, tip segment 206 c may be frusto-conical (e.g., as shownin FIG. 12), in order to facilitate insertion of introducer catheter 810into a patient and navigation of introducer catheter 810 through thepatient's vasculature, while intermediate segment 206 b and proximalsegment 206 a are substantially cylindrical. It is contemplated,however, that tip segment 206 c may also be substantially cylindrical.

As described above, segments 206 a, 206 b, and 206 c may vary in length,for example with proximal segment 206 a being longer than intermediatesegment 206 b, which is in turn longer than tip segment 206 c. In oneembodiment of the invention, proximal segment 206 a may be about 23.5inches long, intermediate segment 206 b may be about 1.5 inches long,and tip segment 206 c may be about 0.25 inches long.

Similarly, segments 206 a, 206 b, and 206 c vary in durometer, withproximal segment 206 a having a higher durometer than the distalsegment. In particular, proximal segment 206 a has a higher durometerthan intermediate segment 206 b, which in turn has a higher durometerthan tip segment 206 c. For example, proximal segment 206 a may have adurometer of 72 D, intermediate segment 206 b may have a durometer ofabout 55 D, and tip segment 206 c may have a durometer of about 35 D.

As best seen in FIG. 11, distal end 890 of introducer 810 may be shapedinto a preset curvature. One preferred preset curvature has a radius ofbetween about 0.8 inches and about 1.2 inches, more preferably betweenabout 0.9 inches and about 1.1 inches, and most preferably of about 1inch, while the arc of the curvature is preferably between about 25degrees and about 45 degrees, more preferably between about 30 degreesand 40 degrees, and most preferably about 35 degrees. It iscontemplated, however, that other preset curvatures may be utilizedwithout departing from the spirit and scope of the present invention.For example, distal end 890 of introducer catheter 810 may be shapedinto any desired curvature for a particular application of introducercatheter 810, for example cardiac ablation.

FIGS. 14 and 15 illustrate an introducer assembly 900 according toanother embodiment of the present invention. In particular, FIGS. 14 and15 illustrate an introducer catheter 910 including a flared transitionsection 912 at its proximal end 914 (e.g., proximate where introducercatheter 910 is coupled to hub 108). Such a transition section isdesirable where the introducer catheter 910 is as large as at leastabout 12 French, but may of course be practiced in connection withcatheters and introducer catheters of other sizes without departing fromthe spirit and scope of the present invention.

As illustrated to good advantage in FIGS. 14 and 15, flared transitionsection 912 may be a frusto-conical section that permits a gradualreduction in the lumen diameter of introducer catheter 910. The lumendiameter of introducer catheter 910 will be larger proximal oftransition section 912 than distal of transition section 912. Typically,the lumen diameter of introducer catheter 910 will be between about0.004″ and about 0.005″ larger proximal of transition section 912 thandistal of transition section 912, though other deltas are within thescope of the present teachings. Preferably, the slope of the transitionsection 912 is between about 4 degrees and about 6 degrees, and morepreferably is about 5 degrees. Of course, other angles may be utilizedconsistent with the present teachings.

The smooth (or funnel-like) transition facilitated by flared transitionsection 912 advantageously permits introduction of larger medicaldevices into the patient without such devices getting “hung up” withinthe hub and without increasing the outer diameter of the section of theintroducer catheter that is introduced into the patient. This may beparticularly desirable, for example, where a large inflatable member,such as a 30 mm balloon, is to be introduced through introducer catheter910.

Although several embodiments of this invention have been described abovewith a certain degree of particularity, those skilled in the art couldmake numerous alterations to the disclosed embodiments without departingfrom the scope of this invention. For example, one of ordinary skill inthe art will appreciate that the features and principles disclosedherein could be practiced in various combinations depending on the needsof a particular procedure (e.g., an introducer catheter including both aflared transition section and a curved distal end, an introducercatheter including a flared transition section that varieslongitudinally in hardness, and the like). One of ordinary skill willalso recognize that the teachings herein may be applied to catheters andintroducer catheters of varying size, shape, and characteristic (e.g.,varying lengths, outer diameters, curvatures, hardnesses, and the like).

In addition, though the invention has been described primarily inconnection with braided flat wires, it is contemplated that the torquetransfer layer may include one or more non-flat wires (e.g., roundwires) and/or one or more helically-wound wires in addition to or as analternative to braided flat wires. Likewise, materials other thanstainless steel (e.g., Kevlar fibers) may be utilized in the torquetransfer layer without departing from the scope of the presentteachings.

All directional references (e.g., upper, lower, upward, downward, left,right, leftward, rightward, top, bottom, above, below, vertical,horizontal, clockwise, and counterclockwise) are only used foridentification purposes to aid the reader's understanding of the presentinvention, and do not create limitations, particularly as to theposition, orientation, or use of the invention. Joinder references(e.g., attached, coupled, connected, and the like) are to be construedbroadly and may include intermediate members between a connection ofelements and relative movement between elements. As such, joinderreferences do not necessarily infer that two elements are directlyconnected and in fixed relation to each other.

It is intended that all matter contained in the above description orshown in the accompanying drawings shall be interpreted as illustrativeonly and not limiting. Changes in detail or structure may be madewithout departing from the spirit of the invention as defined in theappended claims.

What is claimed is:
 1. An introducer catheter having a distal end and aproximal end, comprising: an inner liner having a cylindrical distalsection, a cylindrical proximal section, and a frusto-conicalintermediate section between the distal section and the proximalsection, wherein the inner liner defines a lumen; a torque transferlayer surrounding at least a portion of the inner liner, wherein thetorque transfer layer terminates proximal to the frusto-conicalintermediate section; and an outer sheath surrounding at least a portionof the torque transfer layer, wherein the cylindrical distal section ofthe inner liner defines a distal section of the lumen, the cylindricalproximal section of the inner liner defines a proximal section of thelumen, and the frusto-conical intermediate section of the inner linerdefines an intermediate section of the lumen, and wherein the distalsection of the lumen has a first diameter, the proximal section of thelumen has a second diameter greater than the first diameter, and theintermediate section of the lumen has a diameter that tapers from thesecond diameter to the first diameter.
 2. The introducer catheteraccording to claim 1, wherein a thickness of the outer sheathsurrounding the frusto-conical intermediate section is variable along alength of the frusto-conical section between the proximal and distalsections of the inner liner.
 3. The introducer catheter according toclaim 1, wherein the distal end of the introducer catheter is shaped ina preset curvature in a plane including a central longitudinal axis ofthe introducer catheter.
 4. The introducer catheter according to claim1, wherein the torque transfer layer comprises at least two flat wiresbraided into a wire mesh.
 5. The introducer catheter according to claim1, wherein the tapering diameter of the intermediate section of thelumen has a slope between 4 degrees and 6 degrees.
 6. The introducercatheter according to claim 1, wherein an outer diameter of the outersheath is greater at a proximal end of the introducer catheter than at adistal end of the introducer catheter.
 7. The introducer catheteraccording to claim 6, wherein the outer sheath comprises a proximalsection having a first outer diameter, a distal section having a secondouter diameter smaller than the first diameter, and a transition sectionbetween the proximal section and the distal section having an outerdiameter that tapers from the first outer diameter to the second outerdiameter.
 8. An introducer catheter, comprising: an inner liner thatdefines a lumen having a distal section, a proximal section, and anintermediate section, wherein the distal section of the lumen has afirst diameter, the proximal section of the lumen has a second diametergreater than the first diameter, and the intermediate section of thelumen has a diameter that tapers from the second diameter to the firstdiameter; a torque transfer layer surrounding less than an entire lengthof the inner liner; and an outer sheath surrounding at least a portionof the torque transfer layer.
 9. The introducer catheter according toclaim 8, wherein the torque transfer layer terminates proximal to theintermediate section of the lumen.
 10. The introducer catheter accordingto claim 8, wherein the torque transfer layer comprises at least twoflat wires braided into a wire mesh.
 11. The introducer catheteraccording to claim 8, wherein the tapering diameter of the intermediatesection of the lumen has a slope between 4 degrees and 6 degrees.